Helmet Mounted Displays (HMD), or head mounted displays, are display devices worn on the head of a user as part of a helmet. The HMD may be positioned in front of one or both of the user's eyes. Typically, the HMD is configured to reflect images projected on to it, while at the same time allowing the user to see through it.
It is known to use HMDs to display information to the pilot of an aircraft to facilitate the pilot in performing an operation such as landing the aircraft. Such information is often referred to as “HMD symbology”.
HMD symbology for facilitating a pilot of an aircraft to land that aircraft on an aircraft carrier includes: Ship Referenced Velocity Vectors (SRVVs), Ship Referenced Velocity Vector scales (SRVV scales), Flight Path Markers (FPMs), and horizon bars.
Many factors may cause the HMD symbology displayed to a pilot to be erroneous or inaccurate. Such errors and inaccuracies may increase the likelihood of aircraft damage as well as pilot or ground crew injury. Thus, there is a need to determine when displayed HMD symbology is erroneous, and to mitigate the effects of the error.